What I find interesting about grabs in Aikido is not how realistic or unrealistic they are, but how I can possibly turn them into a connection to my partner wherein they cannot let go.

I certainly have spent a lot of time in my training exploring how nikyo comes from uke attempting to prevent this sword draw, and yonkyo is that sword takeway, and so forth, even using 'swords' and certainly find it a fascinating study.

I have also spent a lot of time trying to turn the various grabs into 'real' attacks, pushes or pulls that model various kinds of scenarios.

My personal conclusions are that, while it is important to train and experiment in these ways, it is most important that the attacks legitimately disturb tori/nage/shite's center in some fashion, and that tori/nage/shite should be trying to find ways to alter their physical relationship to uke such that uke cannot let go of tori/nage/shite without falling down or otherwise being exposed to more danger.

In the end, if you are achieving this type of training relationship, it doesn't much matter if the grab is realistic or not, or an unexpected variation or not, because the principles being practiced come out in the infinite variations of actual grabs, pushing, pulling, or even simply crushing.

Just my current thoughts. Ask me again in a few years and they may well be different. Or not.